55 
in their native state and in all stages of development, it can hardl 
be expected that any one should know beforehand what constitutes 
the specific characters in these plants. I have tried to unite the forms 
which seemed to justify such a proceeding (see, e. g. O. Rafinesquii, 
here made to comprise quite a suite of forms as subspecies). Still it 
may be thought that a greater reduction was yet desirable ; but with 
our present data this would involve great danger of jumbling hetero- 
geneous materials together. Nos. 5 and 7 (of which latter neither 
flower nor fruit is known) can perhaps be united; also 9 and 10, 11 
and 12,13 and 14, 16 and 17, 19 and 20, 22 —24, 25-28, 29 and 
30, 31 — 33, 35 —- 37, 388-40, and 48 and 49, — leaving 31 types, 29 
of which are indigenous to our territory, and two cultivated. 
Geography of the Cactus Region of the United States. 
The localities where our Cacti grow are so little known to those 
who have not made the geography of the West a particular study, or 
are familiar with the publications of our Western explorers, that it 
seems necessary to add a few explanatory remarks. 
Texas, as at present organized, is bounded southeasterly by the 
Gulf of Mexico, into which the following rivers mentioned in the fore- 
going pages empty, following the order from east to west: the Brazos, 
the Colorado with the Llano, the Guadalupe with the Pierdenales 
and San Antonio, the Nueces, and the Rio Grande. The latter forms — 
the southern and southwestern boundary as high up as El Paso. 
it are the towns of Matamoras (not far from its mouth), Mier, Lare- 
do ; and higher up, Presidio del Rio Grande ; then Fort Duncan or 
Eagle Pass (southwest of which is Santa Rosa, in the State of Coa- 
huila) ; next comes the mouth of the San Pedro or Devil’s River 
(a small river or rather torrent running southward), and not far from 
it the mouth of the Pecos or Puerco, which rises at the north-north- 
west in the upper parts of New Mexico. Between the mouth of the 
Pecos and El Paso we notice only Presidio del Norte, San Elizario, 
and a “ cajion ” below the latter. The valley of the Limpio, a little 
more to the northward between the Pecos and El Paso, is a remark- 
able locality ; probably because there porphyritic rocks take the place 
of the cretaceous formation of the more eastern districts. 
Chihuahua is the well-known capital of the Mexican State of the 
same name, south of El Paso. 
